Small, cheap MPPT?

basewindow

Has anyone had experience with or can anyone give an opinion on this MPPT CC

http://www.ebay.com.au/itm/281040186808?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

My system is fairly small and unlikely to expand beyond another 120w panel any maybe another 100ah of battery somewhere down the line.

I would like a Midnite or Outback but can't justify the cost or benefit.

So for a spare CC or to replace my 30A PWM when it dies, is something like this reasonable?

Eric L

Re: Small, cheap MPPT?

Can't speak to that one, but after efficiency losses, your proposed 360 watts of panel will rarely be putting out much more than 20 amps into a 12 volt bank at typical charging voltages (13-15 v).

I'm saying this because NAWS has these Blue Sky MPPT controllers on clearance that do 20 amps at 12v. 5 year warranty on them. Don't know if it makes sense to ship to AU though.

http://www.solar-electric.com/diblskysbmps.html

Edit to add; it looks like they have a 25 amp model for even less, but this one requires a low input voltage (paralleled 12 volt panels only):

http://www.solar-electric.com/sbchco2512vm.html

niel

Re: Small, cheap MPPT?

often times you are taking a big chance with some of that stuff. it may even be mislabeled and not be an mppt cc at all and it could even fall short on its specs. 2yr warranty? right, good luck on that.

westbranch

Re: Small, cheap MPPT?

Being in Oz, I suspect that you rarely get any cold temps, ie < -1*C, so the benefit of an MPPT CC will be low.

If you are unhappy with the current CC you might try looking into some of the Morning Star PWM CC's, possibly one per panel if you are not going to add more PV.

hth

Cariboocoot

Re: Small, cheap MPPT?

I see no benefit in buying an "MPPT" controller that offers no benefit over a PWM controller, and it doesn't look like this one does. That need for panel Vmp to be 'right' for nominal system Voltage sounds like it lacks the ability to down-convert higher Voltage to greater current. Some of the Blue Sky controllers have this sort of limitation and I wouldn't recommend them either.

A good MPPT controller will let you put a range of Voltage on its input from Vmp minimum for the system Voltage on up to a maximum. So you could use Vmp 35 panels with a 24 Volt system or with a 12 Volt system. As long as the input V was above the charging point of the battery it should work. If it won't, it's not a very good "MPPT" controller.

Another trick sellers use is to report higher power output from MPPT based on cold temps raising panel Voltage, and imply this occurs all the time. Then you get those "20% more power over PWM" claims which aren't true because panels do not operate cold most of the time. Even up here where the PV can superconduct it doesn't happen all the time and the yearly power gain from this phenomenon does not average out to any miraculous increase over PWM.

MPPT's major advantage is not in greater power realized over PWM but in greater flexibility in array configuration. If the controller is going to limit you to "12 V panel with 12 V system" it isn't really offering any advantage at all.

newl

Re: Small, cheap MPPT?

I'd be cautious of their usage of the "MPPT" acronym, especially at that price. I remember when I started out almost getting sucked in which is why I intentionally stepped back to PWM and then into my Tristar 45 MPPT, both of which were known to be true and valid units.

john p

Re: Small, cheap MPPT?

If you in Australia go to a JAYCAR store and buy this one its one of the best most reliable PWM controlers available. Virtually indestructible.. Its a great Chinese copy of an old Steca design
Have used many of them ,their very adjustable to suit your batteries needs.
www.jaycar.com.au
model MP3129

basewindow

Re: Small, cheap MPPT?

My 30a PWM is still working fine after 3 years, but I really just wanted a spare (and MPPT seems to be the way things are going) or in the event that I wanted to change the panel configuration to 24v and down convert.

I guess at these wattages I'm not going to see too much benefit from a MPPT anyway. A Tristar 45 would be great but then again it's about $400 over here.

I guess this is the same thing under different brand

http://www.ebay.com.au/itm/POWERTECH-12V-24V-30A-MPPT-Solar-Regulator-Charge-Controller-LATEST-MODEL-/221165053877?pt=AU_Solar&hash=item337e76e7b5&_uhb=1

It was just a thought.

Thanks.

basewindow

Re: Small, cheap MPPT?

John p, believe it or not that one from Jaycar is pretty much what I have at the moment, except in the 30A version. Different name on it, but that's it.

As I said it's working fine and doing everything it's supposed to. I just wanted a spare in the event of a failure and thought perhaps one of these 'so called' MPPT ones might have been a good alternative.

Cheers.

YehoshuaAgapao

Re: Small, cheap MPPT?

The closest to a cheap, small, true-MPPT you will get is probably the MorningStar SunSaver 15A MPPT charge controller. $225 at NAWS. Half the price, quarter the capacity.

peterako

Re: Small, cheap MPPT?

I received with my solar panels two pcs for free from manufacturer.

They are PWM not MPPT i can see it on the charge current, it works but not efficient.